1. Field of the Invention
The present invention relates to a backing-up apparatus, a backing-up method, and a backing-up program.
2. Description of the Related Art
Conventionally, OPC (One Point Copy) is known as one of the approaches of backing up a copying origin volume in a storage device or a computer. OPC produces a snapshot that is data at a predetermined time point (not incorporating updates thereafter, etc.) for the data to be backed up and. More specifically, when a backup is produced, OPC is an approach of backing up the whole data of a copying origin volume that is the target at the time of the production.
For example, when a backing-up apparatus that executes OPC receives an OPC instruction to execute OPC from a user, the apparatus duplicates or copies the whole data of a copying origin volume that is present at the time when the OPC instruction has been received. The backing-up apparatus stores the duplicated data (backup data) as the snapshot at the time when the OPC has been received. Describing taking a specific example, the backing-up apparatus stores the backup data that is the data obtained by duplicating the whole copying origin volume in accordance with the time point at which the apparatus has received the OPC instruction and the generation information (session information).
An approach called “SnapOPC” is known as one of expanded functions for the above-mentioned OPC. SnapOPC is an approach of backing up only the data before updating in the place to which the updating has been executed in the data of the copying origin volume when a backup is produced.
For example, when a backing-up apparatus that executes SnapOPC receives a SnapOPC instruction to execute SnapOPC, the backing-up apparatus allocates a predetermined storage area correlating the area with the time point at which the apparatus has received the SnapOPC instruction and the generation information (session information). When updating is executed to the copying origin volume after the SnapOPC instruction has been received, only the data before the updating in the place to which the updating has been executed (the differential data that has been lost from the copying origin volume due to the execution of the updating) is duplicated and is stored in the storage area. Japanese Patent Application Laid-Open Publication No. 2005-292865 discloses one of the approaches of storing differential data.
The above conventional technique has a problem that a data transfer amount can not be reduced as described below.
For example, in the above conventional OPC, as to the copying origin volume at the time when the OPC instruction has been received, the whole data of the copying origin volume is copied for each time point at which such an instruction has been received. Therefore, the backing-up apparatus that executes the OPC copies and transfers the whole data of the copying origin volume for each time point at which an OPC instruction is issued. Therefore, the data amount to be transferred is tremendous.
For example, in the above conventional SnapOPC, as shown in FIG. 27, in the case where a plurality of SnapOPC instructions are issued, when first updating is executed in a place in the original data, the data before the updating in the place is transferred to and stored in each storage area allocated in each session executed before the updating. Therefore, the data amount to be transferred is tremendous. FIG. 27 is an explanatory view of the conventional SnapOPC.
Description will be given for the case, as a specific example, where, in the conventional backing-up apparatus that executes SnapOPC, a SnapOPC instruction is issued for three times by a user and, thereafter, first updating is executed in a place in the original data. To store a backup at the time when each SnapOPC instructions is issued, the conventional backing-up apparatus that executes SnapOPC transfers and stores each data before each updating in the place to/in each of the storage areas (each of a total of three storage areas) allocated being correlated with the session information for each of the three SnapOPC instructions. The approach of the above publication (Japanese Patent Application Laid-Open Publication No. 2005-292865) does not reduce the data amount to be transferred.